Why do some people have DF and others have DHF, although same flaviviruses cause both?
It is not clear with certainity why does DHF occur in some cases when the most have only dengue fever. It .is suggested that when there are circulating antibodies against one serotype due to earlier infection and later there is infection with another serotype, it may result in dengue hemorrhagic fever / dengue shock syndrome. The risk of DHF is 0.2% during the first dengue infection but it increases 10-fold during infection with a second serotype of dengue virus. However, the circulation of multiple dengue serotypes does not always produce DHF.
